Since SO exists for the readers and not just the asker, I think that makes it even more important to highlight all the reasons not to do X if it really is unlikely to be the best solution.

Maybe the asker really would be best suited with X due to some contrived circumstance, but is that true of everyone else who finds the thread too? Probably not.

I just don't see why it's a problem to add a caveat in the answer in that case.

I.e. "you can do X to achieve your goal, but you probably shouldn't because Y".

I just don't see how it's helpful or contributive to participate in the discussion if you don't actually know the answer.